Methods and apparatus for indicating a polishing tape end

ABSTRACT

Apparatus and methods are provided for polishing a substrate with a polishing tape. The polishing tape includes a first surface adapted to contact a substrate; and a second surface, wherein at least one of the first and second surfaces include a feature adapted to indicate an end condition. Numerous other aspects are provided.

FIELD OF THE INVENTION

The present invention relates generally to substrate processing, and more particularly to methods and apparatus for indicating a polishing tape end.

BACKGROUND OF THE INVENTION

Substrates are used in electronic device manufacturing. During processing, a film may be deposited on the surface of a substrate. However, it may be undesirable to have a film on the edge of the substrate, as it may negatively affect the electronic devices formed on the substrate. The film may be removed by polishing the substrate edge with, for example, a polishing pad or tape, or any other suitable polishing means. The polishing tape may be housed on spools. Accordingly methods and apparatus for efficiently and effectively determining an endpoint of the polishing tape are desirable.

SUMMARY OF THE INVENTION

In some aspects of the invention a polishing tape for polishing a substrate is provided. The polishing tape includes a first surface adapted to contact a substrate; and a second surface, and wherein at least one of the first and second surfaces include a feature adapted to indicate an end condition.

In other aspects of the invention, a system for polishing a substrate is provided. The system includes a substrate support; and a polishing apparatus. The polishing apparatus includes a housing including: at least one supply spool; at least one take-up spool; a polishing tape, wherein the polishing tape is adapted to advance between the supply and take-up spools. The polishing tape includes: a first surface adapted to contact a substrate; and a second surface, and wherein at least one of the first and second surfaces include a feature adapted to indicate an end condition of the polishing tape. The system also includes a controller adapted to determine the end condition of the polishing tape based on the feature.

In yet other aspects of the invention, a method is provided for determining a polishing tape end condition. The method includes (1) advancing a polishing tape from a supply spool to a take-up spool; (2) detecting a feature on a portion of the polishing tape; and (3) determining the feature is a polishing tape end condition.

Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claim and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of an embodiment of a system for polishing parts of a substrate in accordance with the present invention.

FIG. 2 is a schematic illustration depicting an example embodiment of a substrate cleaning apparatus according to the present invention.

FIG. 3 is a schematic illustration of a tape cassette according to the present invention.

FIG. 4A is a schematic illustration of an exemplary embodiment according to the present invention.

FIG. 4B is a schematic illustration of the exemplary embodiment of the present invention shown in FIG. 4A.

FIG. 5A-D are schematic illustrations of exemplary embodiments of end marks according to the present invention.

FIG. 6 is a flow chart depicting an exemplary method according to some embodiments of the present invention.

FIG. 7 is a flow chart depicting another exemplary method according to some embodiments of the present invention.

FIG. 8 is a schematic illustration of polishing tape including marking features according to the present invention.

DETAILED DESCRIPTION

As described above, polishing tape may be used to polish a surface of a substrate. Typically, the polishing tape is wound around spools. As described further below, in some embodiments of a polishing apparatus, the polishing tape may by supplied by a supply spool and then be routed to a take-up spool. The polishing tape may be tensioned between the supply spool and the take up spool, which may provide a tension force to polish the substrate. If the polishing apparatus cannot complete the polishing operation for a particular substrate because the polishing tape has run out or been completely used, the substrate is typically disposed of as scrap. Therefore, it is desirable to know when the polishing tape on the supply spool is approaching the end of the polishing tape. Typically, a user measures, with a caliper, for example, the outer diameter of a spool or roll of polishing tape, and then, for a given polishing tape thickness, the user is able to calculate the length of the polishing tape, and track the polishing tape endpoint by use of a motor encoder on the supply spool, for example. These measurements and calculations may need to be performed for every spool of polishing tape installed on the polishing apparatus, which may be time consuming and costly. Additionally, because the polishing tape endpoint is an estimate, typically based on tolerance analysis, the end of polishing tape condition estimate has an error of approximately plus or minus 18m of tape. Typically 1 m of polishing tape is used to polish each substrate, although 1 m of polishing tape may be used to polish 2 substrates, or any other suitable number of substrates. Thus, the user may typically stop using the polishing tape from a particular spool when it's estimated that approximately 18 m of tape are left on the spool. Consequently, plus or minus 18m of tape may be wasted due to errors in calculation. Additionally, the actual length of polishing tape provided by the supplier, the thickness tolerances, and the tension of the spooled polishing tape may provide additional errors in the polishing tape endpoint determination.

In some embodiments, the present invention provides apparatus and methods to more efficiently determine an end of polishing tape condition. In the present invention a polishing tape end may include a feature that may be detected by a sensor, for example. The detected feature may allow the end of polishing tape condition to be determined to within plus or minus 1 m, for example, which may be approximately equivalent to only 1 substrate in wasted polishing tape. It is noted that the apparatus may typically need to maintain a polishing tape tension between the supply and take-up spools, so it may not be desirable to use all or substantially all of the polishing tape on the supply spool. Consequently the apparatus may be designed to determine a polishing tape end to be within 1-2 m, for example, before the physical end of the polishing tape is approached. The polishing tape feature may include, for example, an optical contrast or color marking, compared to the unmarked polishing tape, laser markings or cut-outs in the polishing tape, a bar code, or any other suitably identifiable feature. The polishing tape feature may allow for efficient polishing tape usage, which may safeguard against substrate scrap, thereby reducing the cost of operation of the polishing apparatus.

In some embodiments, the polishing tape feature may also be used as a length marker at the start of the polishing tape for the purpose of calculating the outer spool diameter, thickness of the polishing tape, or length of the polishing tape, or for calibration purposes, for example.

FIG. 1 is a schematic plan view of an exemplary embodiment of a system 100 for polishing a portion of a substrate 102, such as a substrate edge 104, and/or a substrate notch (not shown). The system 100 of FIG. 1 includes three polishing apparatuses 108, each including a polishing head 110. However, any number and type of apparatus 108/heads 110 may be used in any practicable combination. In addition, in such multi-head embodiments, each head 110 may use a differently configured or type of polishing tape (e.g., different grits, materials, tensions, pressures, etc.) to contact and polish the substrate edge 104 and/or notch. Any number of heads 110 may be used concurrently, individually, and/or in any sequence. The heads 110 may be disposed in different positions and/or in different orientations (e.g., aligned with the substrate edge 104 and/or notch, normal to the substrate edge 104 and/or notch, angled relative to the substrate edge 104 and/or notch, etc.) to allow polishing tape, pushed by a polisher in some embodiments (FIG. 2), to polish different portions of the substrate edge 104 and/or notch.

In some embodiments, one or more of the heads 110 may be adapted to be oscillated or moved (e.g., angularly translated about a tangential axis of the substrate 100 and/or circumferentially relative to the substrate 100) around or along the substrate edge 104 and/or notch so as to polish different portions of the substrate edge 104 and/or notch. In some embodiments, one or more of the heads 110 may be adapted to continuously or intermittently oscillate between the various positions. Alternatively, one or more of the heads 110 may be fixed and/or only adjusted while the substrate 102 is not being rotated. In yet other embodiments, the substrate 102 may be held fixed while one or more of the heads 110 oscillate (as described above) as well as rotate circumferentially around the substrate 102. This movement may be under the direction of a programmed or user operated controller 112, described below. Different heads 110 may be used for different substrates 102 or different types of substrates 102.

As described above, the system 100 may further include the controller 112, (e.g., a programmed computer, a programmed processor, a microcontroller, a gate array, a logic circuit, an embedded real time processor, etc.), which may control the driver(s) used to rotate the substrate 102 and/or the actuator(s) used to push a polisher (FIG. 2) against the substrate edge 104 and/or notch. Note that the controller 112 may be coupled (e.g., electrically, mechanically, pneumatically, hydraulically, etc.) to each of a plurality of actuators. Likewise, the controller 112 may be adapted to receive feedback signals from one or more drivers and/or actuators, that indicate the amount of energy being exerted to rotate the substrate 102 (e.g., rotate a vacuum chuck holding the substrate 102) and/or actuate the actuator(s) to push the polishing pad(s) against the substrate 102. These feedback signals may be employed to determine when a particular layer of film has been removed from the edge 104 and/or notch of the substrate 102 and/or whether a sufficient amount of substrate polishing has occurred.

As mentioned above, substrate polishing may be performed using one or more polishing apparatuses 108. In one or more embodiments, a plurality of polishing apparatuses 108 may be employed, in which each polishing apparatus 108 may have similar or different characteristics and/or mechanisms. In the latter case, particular polishing apparatuses 108 may be employed for specific operations. For example, one or more polishing apparatuses 108 may be adapted to perform relatively rough polishing and/or adjustments while another one or more polishing apparatus 108 may be adapted to perform relatively fine polishing and/or adjustments. Polishing apparatuses 108 may be used in sequence so that, for example, a rough polishing procedure may be performed initially and a fine polishing procedure may be employed subsequently as needed or according to a polishing recipe. The plurality of polishing apparatuses 108 may be located in a single chamber or module, as shown herein, or alternatively, one or more polishing apparatuses 108 may be located in separate chambers or modules. Where multiple chambers are employed, a robot or another type of transfer mechanism may be employed to move substrates 102 between the chambers so that polishing apparatuses 108 in the separate chambers may be used in series or otherwise.

Turning to FIG. 2, a schematic perspective view of an embodiment of a polishing apparatus 200 for polishing a substrate 102 is provided in accordance with the present invention. The polishing apparatus 200 may include a substrate driver 202 (e.g., a servomotor, gear, belt, chain, etc.), which may be mounted on a pedestal 204. A support 206 (e.g., a vacuum chuck) may be coupled (e.g., rigidly) to a shaft (not shown) of the substrate driver 202. The support 206 may support the substrate 102, for example. The substrate driver 202 may rotate the substrate 102, via the support 206, about a center 208 of the substrate 102 or another suitable axis. The substrate driver 202 may be connected to a substrate driver control unit (not shown), which may control the angular displacement, angular velocity, and angular acceleration of the substrate 102. The polishing apparatus 200 may further include a polishing arm 210 aligned in the horizontal plane approximately tangential to the substrate edge 104 and supported by a frame 212. In other embodiments, the polishing arm 210 may be aligned differently, for example, vertically or at an angle with respect to the horizontal plane. The polishing arm 210 may include a polishing head section 214 (‘head’). The polishing head 214 may include a polisher 216, which may be moved towards or away from the substrate 102 by an actuator (e.g., hydraulic actuator, pneumatic actuator, servomotor, etc.) (not shown). The polisher 216 may be relatively or substantially planar in shape, as shown herein, or the polisher 216 may be wheel or roller-shaped. Any other suitable shape may be used. Polishing tape 218, may wrap around the polishing head 214, and over the polisher 216, and be tensioned between spools housed in a cassette 300. In some embodiments, one cassette may be supplied per polishing head 214. The spools may be driven by spool drivers 220, 222 (e.g., servomotors), respectively. The spool drivers 220, 222, may be indexed to precisely control the amount of the polishing tape 218 that is advanced over the polishing head 214 from, for example, the spools, in order to polish the substrate 102.

In one or more embodiments, the polishing tape 218 may be made from many different materials, such as aluminum oxide, silicon oxide, silicon carbide, etc. Other materials may also be used. In some embodiments, abrasives used may range, for example, from about 0.1 microns up to about 10 microns in size or, for example, from about 0.5 microns to 3 microns in size, although other sizes may be used. Different widths of polishing tape 218 ranging from about 0.55 inch to about 1.5 inches may be used, although other polishing tape widths may be used. In one or more embodiments, the polishing tape 218 may be about 0.002 to about 0.02 inches thick and withstand about 1 to 5 lbs. in tension. Other polishing tapes having different thicknesses and tensile strengths may be used.

Turning to FIG. 3, an exemplary schematic illustration of the tape cassette 300 is provided. The cassette 300 may include a body portion 302 and a head portion 304. The cassette body 302 may house a supply spool 306 and a take-up spool 308. While only one supply and take-up spool 306, 308 are shown herein, other numbers of supply and take-up spools may be used. The cassette body 302 may include a selectively removable cover 301 (FIG. 2). The supply spool 306 may store unused polishing tape 218 available to be unwound and pulled into the polishing apparatus 200, positioned adjacent the substrate 102, while the take-up spool 308 may be adapted to receive used and/or worn polishing tape 218. One or both of the supply and take-up spools 306, 308 may be indexed to precisely control the amount of polishing tape 218 that is advanced to the polishing apparatus 200. In alternate embodiments, the polishing tape 218 may be continuously moving. In some embodiments, the take-up spool 308 may advance at a particular speed, and the supply spool 306 may create the tension. A tape loop 310 may indicate the portion of polishing tape 218 that is routed around the polishing head 214, shown in FIG. 2. The cassette body 302 may also include a plurality of rollers 312 to further guide and route the polishing tape 218 through the cassette 300.

The supply and take-up spools 306, 308 may have a diameter of approximately 3 inches and be capable of holding about 30,000 inches of polishing tape 218, or may be a diameter of approximately 1 inch and be capable of holding about 500 inches of polishing tape. Other spool dimensions may be used. The supply and take-up spools 306, 308 may be constructed from materials such as polyurethane, polyvinyl difluoride (PVDF), etc. Other materials may also be used. In some embodiments the supply and take-up spools 306, 308 may be formed by selectively coupling two flanges (not shown) to a core 314 (FIG. 4A), where the supply of polishing tape 218 is wound around the core 314, and each of the two flanges is coupled to opposite ends of the core 314.

Turning to FIGS. 4A and 4B, a schematic view of an exemplary embodiment of the present invention is provided. As described above, it may be desirable to know when the polishing tape 218 on the supply spool 306 is approaching the end of the polishing tape 218. To this end, the polishing tape 218 may include an end mark feature 400 (hereinafter referred to as “end mark”). The end mark 400 may be coupled to or integrally formed with the polishing tape 218, for example. The end mark 400 may be the polishing tape end condition, or at least used to indicate the polishing tape end condition.

In some embodiments, the end mark 400 may be on a non-abrasive side of the polishing tape 218. It may be desirable to include the end mark 400 on the non-abrasive side of the polishing tape to prevent the end mark 400 from contaminating the polishing tape 218. If the polishing tape 218 is contaminated by the end mark 400, the contaminants may spread to the substrate 102 during a polishing process, which may cause the substrate 102 to be unusable. It should be noted that even with the end mark 400 included on the non-abrasive side of the polishing tape 218, the end mark 400 may still contact the abrasive side of the polishing tape 218, as the polishing tape 218 may be wound around the core 314. However, the end mark 400 may have an acceptable metal contamination level, making contact between the end mark 400 and the abrasive side of the polishing tape 218 inconsequential. In other embodiments the end mark 400 may be on an abrasive side of the polishing tape 218. The end mark 400 may be formed from a laminated film, for example, which may be adhered to the polishing tape 218, for example. Any other suitable means to attach the end mark 400 to the polishing tape 218 may be used. The laminated film may be, for example, PET, nylon, boPET (mylar), polyimide, vinyl, acrylic, or a silicon based material. Any other suitable material may be used. The end mark 400 may have a thickness of between 0.0002 and 0.005 inches, for example. Other suitable thicknesses may be used.

In other embodiments, the end mark 400 may be formed by laser markings, or cut-outs (FIG. 5D) on the polishing tape 218, or may be a material embedded during the formation of the polishing tape 218, for example. Any other suitable end mark 400 may be used.

The apparatus 200 may also include an end mark sensor 402 adapted to detect the end mark 400. The end mark sensor 402 may be an optical non-contact sensor, for example, or any other suitable sensor. It may be desirable to have a non-contact sensor to prevent contamination of the polishing tape 218. The end mark sensor 402 may be housed or positioned within the cassette 300, or any other suitable location. The end mark sensor 402 may be able to detect contrast between different colors (FIG. 5A), textures (FIG. 5B), thickness (FIG. 5C) or cut-outs (FIG. 5D), for example, of the end mark 400 compared to the polishing tape 218. In some embodiments, the end mark sensor 402 may detect color wavelengths associated with the end mark 400. Other suitably detectable end mark features may be used. In some embodiments, an ultrasonic sensor 316 may measure in real time an outer diameter (measure of diameter of polishing tape 218 spooled on supply spool 306,) of the polishing tape 218. The dashed line may indicate a decreasing outer diameter compared to the solid lines.

Turning to FIG. 6, an exemplary method 600 for determining a polishing tape end condition is provided. In step S602, the polishing tape 218 advances from the supply spool 306 to the take up spool 308. In some embodiments, the speed with which the polishing tape 218 advances may be based on a polishing process recipe or steps, for example, or on other parameters, such as an optimized polishing speed, for example. In step S604, the end mark sensor 402 may detect a feature on the polishing tape 218. As described below, the feature may be the end mark 400. In alternate or additional embodiments, the feature may be a reference feature 800 (FIG. 8). The end mark sensor 402 may send a signal to the controller 112 regarding the polishing tape 218. In some embodiments, the controller 112 may compare the received end mark sensor signals to each other and determine if a difference exists between the end mark 400 or reference feature portion of the polishing tape 218 and the non-end mark/reference feature portion of the polishing tape 218. As described above, the end mark 400 may be a different color from the polishing tape 218, for example, and the end mark sensor 402 may detect the different wavelengths or contrast of the end mark 400 compared to the polishing tape 218; or the end mark 400 may be a different thickness from the polishing tape 218, for example, and the end mark sensor 402 may be a micrometer, for example, which may detect the end mark 400. In step S606, the controller 112, for example, may determine whether the detected feature is the end mark 400. In some embodiments, the controller 112 may determine the detected feature is the end mark 400 based on the number of preceding detected reference features, for example, the type of feature, or some other parameter associated with the end mark 400. If the detected feature is the end mark 400, the advancement of the polishing tape 218 may end in step S608.

Turning to FIG. 7, another exemplary method 700 for determining a polishing tape feature is provided. In some embodiments, the polishing tape 218 may include features in addition to (or instead of) the end mark 400. These other features may include, for example, a first, lead, calibration or reference mark 800 (FIG. 8) and a second calibration or reference mark 802 (FIG. 8). In some embodiments, the first and second reference marks 800, 802 may be used for calibration, for example. Typically, a polishing tape supplier may provide information on a label or certificate related to an outer supply spool diameter (measure of diameter of polishing tape 218 spooled on supply spool 306), thickness and/or length of polishing tape 218 on the supply spool 306. However, the supplier may include more or less polishing tape 218 on the supply spool 306 than requested or indicated on the label, as there may be a tolerance of, for example plus or minus 5 meters of polishing tape 218. Other tolerances may be used. Calibration may be used to confirm the amount of polishing tape 218, and allow for corrections of the information provided by the supplier, for example. In step S702, a portion or length (L1) (FIG. 8) of the polishing tape 218 between an end 804 (FIG. 8) of the polishing tape 218 and the first reference mark 800 is threaded or advanced into the polishing apparatus 200. The lead portion L1 may be non-abrasive, for example, as this lead portion L1 may not be used to polish the substrate 102. Alternatively, the lead portion L1 may be abrasive. A mark sensor, such as the end mark sensor 402, for example, may detect the first reference mark 800, in step S704. In step S706 the polishing tape 218 advances. In step S708, the mark sensor 402 may detect the second reference mark 802. In step S710, encoders 806 (FIG. 2) may be calibrated based on the detection of the second reference mark 802. The length (L2) of tape between the first reference mark 800 and the second reference mark 802 may define a length of polishing tape 218 that may be used to calibrate one or more encoders 806 (FIG. 2), such as motor encoders, for example. The motor encoders 806 may be coupled to spool drivers 220, 222 of the supply and take-up spools 306, 308, for example. The motor encoders 806 may count the number of revolutions of the supply and take-up spools 306, 308. The encoders 806 may also be coupled to the controller 112 (FIG. 1), for example, whereby the controller 112 may be adapted to receive a signal indicative of the revolution count. The controller 112 may consider the length L2 of tape between the first and second reference marks 800, 802 as well as the number of revolutions during this length L2, and use this information to calibrate the encoders 806.

As shown in FIG. 8, and as described above, the end mark feature 400 may be positioned a length L3 before a physical end 808 of the polishing tape 218. The length L3 may provide a “warning” before the polishing tape end 808 is reached. In some embodiments, the polishing tape 218 may include more than one end mark feature 400, which may provide several “warnings” at different lengths that the polishing tape end 808 is approaching.

The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art.

Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims. 

1. A polishing tape for polishing a substrate, the polishing tape comprising: a first surface adapted to contact a substrate; and a second surface, and wherein at least one of the first and second surfaces include a feature adapted to indicate an end condition.
 2. The polishing tape of claim 1 wherein the first surface is abrasive and the second surface is non-abrasive.
 3. The polishing tape of claim 2 wherein the feature is included in the second surface.
 4. The polishing tape of claim 1 wherein the feature is optically different from a non-feature portion of the polishing tape.
 5. The polishing tape of claim 4 wherein the optically different feature comprises at least one of thickness, texture and contrast.
 6. The polishing tape of claim 4 wherein the optically different feature comprises a difference in absorption of light wavelengths compared to the non-feature portion of the polishing tape.
 7. The polishing tape of claim 4 wherein the optically different feature comprises at least one of etchings and cut-outs.
 8. The polishing tape of claim 2 further comprising an adhesive, wherein the adhesive is adapted to adhere the feature to the non-abrasive surface of the polishing tape.
 9. The polishing tape of claim 1 further comprising at least two calibration features.
 10. The polishing tape of claim 9 wherein the at least two calibration features are optically different from a non-feature portion of the polishing tape.
 11. A system for polishing a substrate comprising: a substrate support; a polishing apparatus comprising: a housing including: at least one supply spool; and at least one take-up spool; a polishing tape, wherein the polishing tape is adapted to advance between the supply and take-up spools, wherein the polishing tape comprises: a first surface adapted to contact a substrate; and a second surface, and wherein at least one of the first and second surfaces include a feature adapted to indicate an end condition of the polishing tape; and a controller adapted to determine the end condition of the polishing tape based on the feature.
 12. The system of claim 11 wherein the first surface is abrasive and the second surface is non-abrasive.
 13. The system of claim 12 further comprising: a sensor, wherein the sensor is adapted to detect the feature.
 14. The system of claim 13 wherein the controller is adapted to receive a signal from the sensor indicative of the detected feature.
 15. The system of claim 14 wherein the controller is adapted to determine the end condition based on the signal.
 16. The system of claim 12 wherein the feature is optically different from a non-feature portion of the polishing tape.
 17. The system of claim 16 wherein the optically different feature comprises at least one of texture and contrast.
 18. The system of claim 16 wherein the optically different feature comprises a difference in absorption of light wavelengths compared to the non-feature portion of the polishing tape.
 19. The system of claim 11 wherein the polishing tape further comprises at least two calibration features.
 20. The system of claim 19 wherein the at least two calibration features are optically different from a non-feature portion of the polishing tape.
 21. The system of claim 20 further comprising one or more motor encoders adapted to regulate the speed of at least one of the supply and take-up spools.
 22. The system of claim 21 wherein the controller is adapted to calibrate the one or more motor encoders based on the at least two calibration features.
 23. A method for determining a polishing tape end condition comprising: advancing a polishing tape from a supply spool to a take-up spool; detecting a feature on a portion of the polishing tape; and determining the feature is a polishing tape end condition.
 24. The method of claim 23 wherein detecting the feature further comprises: comparing the feature portion of the polishing tape to a non-feature portion of the polishing tape.
 25. The method of claim 23 further comprising: detecting a calibration feature on a portion of the polishing tape; and calibrating a motor encoder based on the detection of the calibration feature. 